JP4447204B2 - Fuel cell with metal separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell comprising a metal separator (e.g., a solid polymer electrolyte fuel cell).
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-228207
A solid polymer electrolyte fuel cell is formed by laminating a module comprising a membrane-electrode assembly (MEA) and a separator. The MEA includes an electrolyte membrane made of an ion exchange membrane, an electrode (anode, fuel electrode) made of a catalyst layer disposed on one surface of the electrolyte membrane, and an electrode made of a catalyst layer placed on the other surface of the electrolyte membrane (cathode, air). Poles). A diffusion layer is provided between the anode side catalyst layer and the separator and between the cathode side catalyst layer and the separator. A fuel gas flow path for supplying fuel gas (hydrogen) to the anode is formed in the separator on the anode side of the MEA, and oxidizing gas (oxygen, usually air) is supplied to the cathode on the separator on the cathode side of the MEA. An oxidizing gas flow path is formed. A stack is configured by arranging terminals, insulators, and end plates at both ends of the module stack in the module stacking direction, the stack is tightened in the module stacking direction, and a fastening member (e.g., extending in the module stacking direction outside the module stack) Tension plate) and bolts.
In a solid polymer electrolyte fuel cell, a reaction for converting hydrogen into hydrogen ions and electrons is performed on the anode side, the hydrogen ions move through the electrolyte membrane to the cathode side, and oxygen, hydrogen ions and electrons (adjacent to the cathode side). Of water generated from the anode of the MEA's anode through the separator, or the electron generated at the anode of the cell at one end of the module stack through an external circuit to the cathode of the cell at the other end of the module stack) Is done.
Anode side: H ₂ → 2H ⁺ + 2e ⁻
Cathode side: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O
In order to cool the Joule heat and the heat in the water generation reaction at the cathode, a refrigerant flow path through which a refrigerant (usually cooling water) flows is formed between the separators to cool the fuel cell.
Japanese Patent Application Laid-Open No. 2000-228207 discloses a metal separator in which a separator is formed from a metal by press molding, a reaction gas is supplied to the front surface, and cooling water is supplied to the back surface. In the separator of this publication, the refrigerant flow path width is larger than the gas flow path width from the drawing. In addition to this publication, in the case of a metal separator, the refrigerant flow path width is larger than the gas flow path width in actual production.
[0004]
[Problems to be solved by the invention]
However, in a separator that forms a flow path by press molding, such as a metal separator, when a gas flow path is formed on the front surface, the flow path width and flow path cross-sectional area of the refrigerant flow path on the back surface are uniquely determined. In that case, if the refrigerant flow path width is made larger than the gas flow path width as in the prior art, the following problem occurs.
(i) Since the separator part at the bottom of the groove of the refrigerant flow path is a part that presses the diffusion layer and makes the diffusion of the gas into the catalyst layer worse, if the refrigerant flow path width increases, it can be effectively used as a power generation area in the cell area The area is reduced.
(ii) The amount of cooling water increases, and the metal has good heat conduction, so it is overcooled. Too much cooling tends to cause flooding downstream of the oxidizing gas. In addition, the amount of cooling water increases, the water heat capacity increases, and cooling controllability may deteriorate.
An object of the present invention is a fuel cell in which the channel is provided with a metal separator formed by a press, can increase the effective available surface area as a generator area, and can prevent excessive cooling of the fuel cell, the metal separator It is to provide a fuel cell provided.
[0005]
[Means for Solving the Problems]
The present invention for achieving the above object is as follows.
Comprises a metal separator moiety is that is formed by a press having a portion where the refrigerant flow path is formed on the other surface gas flow path is formed on one surface, the metal separator is in contact with one another in the gas flow path groove bottom between modules In a fuel cell equipped with a metal separator,
The metal separator is
The gas flow path width is constant in the depth direction of the gas flow path except for the metal separator curved portions at both ends in the depth direction of the gas flow path,
The gas channel width d _G at the midpoint position of the gas channel depth and the refrigerant channel width d _W obtained by subtracting the gas channel width d _G from the gas channel pitch D are:
d _G ≧ d _W
Fuel cells having a metal separator, characterized in that satisfies the relationship.
[0006]
In fuel cells having the above metal separator, because you have a d _G ≧ d _W, refrigerant flow path width is reduced than the conventional one.
By reducing the refrigerant flow path width, the area of the diffusion layer pushed by the bottom of the separator refrigerant flow channel groove is reduced, and the area of the poor gas diffusion to the catalyst layer is reduced. The area of the portion (the catalyst layer portion where the gas is sufficiently diffused and supplied) is effectively increased.
In addition, since the coolant flow path width is reduced, the amount of cooling water is reduced, the cells are not excessively cooled, and the heat capacity of the cooling water is also reduced, thereby improving the controllability. By preventing excessive cooling, flooding in the downstream portion of the oxidizing gas due to the generated water is also suppressed.
In the fuel cell separator described above, the flow path forming portion has a large thermal conductivity, and thus cooling tends to be excessive. However, since it is assumed that the above conditions are satisfied, the amount of cooling water is small. Excessive cooling can be prevented.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the fuel cells having a metal separator of the present invention with reference to FIGS. 1 to 3 will be described.
Fuel cell having a main barrel separator of the present invention is a solid polymer electrolyte fuel cell 10. The fuel cell 10 of the present invention is mounted on, for example, a fuel cell vehicle. However, it may be used other than an automobile.
[0008]
As shown in FIGS. 1 to 3, the solid polymer electrolyte fuel cell 10 is formed by stacking a module 19 including a membrane-electrode assembly (MEA) and a separator 18. The MEA includes an electrolyte membrane 11 made of an ion exchange membrane, an electrode 14 (anode, fuel electrode) made of a catalyst layer 12 disposed on one surface of the electrolyte membrane 11, and a catalyst layer 15 disposed on the other surface of the electrolyte membrane 11. Electrode 17 (cathode, air electrode). A diffusion layer 13 is provided between the anode side catalyst layer 12 and the separator 18, and a diffusion layer 16 is provided between the cathode side catalyst layer 15 and the separator 18. The diffusion layer 13 may be considered as part of the anode 14, and the diffusion layer 16 may be considered as part of the cathode 17. A terminal 23, an insulator 21, and an end plate 22 are arranged at both ends of the module stack in the module stacking direction to form a stack 23. The stack 23 is tightened in the module stacking direction, and is placed outside the module stack in the module stacking direction. It is fixed with an extending fastening member 24 (for example, a tension plate) and a bolt 25.
[0009]
A fuel gas flow path 27 for supplying fuel gas (hydrogen) to the anode 14 is formed in the separator 18 on the anode 14 side of the MEA, and an oxidizing gas (oxygen, oxygen, etc.) is supplied to the cathode 17 in the separator 18 on the cathode 17 side of the MEA. An oxidizing gas passage 28 for supplying air (usually air) is formed.
The refrigerant flow path 26 is provided between the separators 18 of adjacent modules, and a refrigerant (usually cooling water) flows through the refrigerant flow path 26 to cool the fuel cell whose temperature is going to rise due to Joule heat and reaction heat. To do. The refrigerant channel 26 is provided on the surface (back surface) opposite to the surface (front side surface) of the separator 18 on the side where the gas channel (fuel gas channel 27 or oxidizing gas channel 28) is provided. Yes.
[0010]
The catalyst layers 12 and 15 are composed of a catalyst component, for example, platinum (Pt), carbon (C) supporting the catalyst component, and an electrolyte.
The diffusion layers 13 and 16 are mainly composed of carbon (C) and have air permeability.
The separator 18 has a portion (18A or 18B) formed with a press in which a gas channel (fuel gas channel 27 or oxidizing gas channel 28) is formed on one surface and a refrigerant channel 26 is formed on the other surface. The part (18A or 18B) formed by pressing is made of metal, for example. However, the portion (18A or 18B) formed by pressing is not limited to metal, and may be a conductive resin formed by pressing. In the following, a case where the portion (18A or 18B) formed by pressing is made of metal is taken as an example.
[0011]
When the part (18A or 18B) formed by pressing is made of metal, the separator 18 is made of metal separators 18A and 18B and resin frames 18C and 18D.
As shown in FIG. 3, when the MEA is sandwiched between the separators 18, resin frames 18 </ b> C and 18 </ b> D in which portions corresponding to the MEAs are hollowed out are arranged on the MEA side of the metal separators 18 </ b> A and 18 </ b> B, respectively. The frame 18C, MEA, resin frame 18D, and metal separator 18B are laminated in this order. Since the resin frames 18C and 18D are hollowed out in the MEA portion, the metal separators 18A, MEA, and the metal separator 18B are stacked in this order, and the MEA portions do not protrude from the resin frames 18C and 18D. The metal separator 18A, the resin frame 18C, the resin frame 18D, and the metal separator 18B are laminated in this order. The MEA part constitutes a power generation part of the fuel cell.
[0012]
The metal separators 18A and 18B are impermeable, and are made of, for example, a metal plate (for example, a stainless steel plate) plated with a good conductive metal (for example, nickel plating).
Metal separator 18A and resin frame 18C separate fuel gas (for example, hydrogen) and refrigerant (for example, cooling water), and metal separator 18B and resin frame 18D have oxidizing gas (for example, oxygen, usually air) and refrigerant. Isolate. In addition, the metal separators 18A and 18B form an electric path through which electrons flow from the anode to the cathode of adjacent cells.
[0013]
A fuel gas channel 27 is formed on one surface of the metal separator 18A corresponding to the fuel cell power generation unit (a surface facing the MEA), and a refrigerant channel (cooling water channel) 26 is formed on the back surface. Yes. Similarly, an oxidizing gas flow path 28 is formed on one surface of the metal separator 18B corresponding to the fuel cell power generation unit (a surface facing the MEA), and a refrigerant flow path (cooling water flow path) 26 is formed on the back surface. Is formed. The unevenness of the gas flow path is formed by press molding.
[0014]
Opposite portions 30, 31 of the metal separators 18A, 18B and the resin frames 18C, 18D that face each other across the fuel cell power generation unit (portion with the MEA) are connected to a refrigerant manifold 32 connected to the refrigerant flow path 26, fuel gas A fuel gas manifold 33 connected to the flow path 27 and an oxidizing gas manifold 34 connected to the oxidizing gas flow path 28 are formed. One of the facing portions 30 and 31 facing each other across the fuel cell power generation unit corresponding portion is provided with an inlet-side refrigerant manifold 32a, an outlet-side fuel gas manifold 33b, and an inlet-side oxidizing gas manifold 34a. 31 is provided with an outlet-side refrigerant manifold 32b, an inlet-side fuel gas manifold 33a, and an outlet-side oxidizing gas manifold 34b.
A rectifying unit 35 is provided between each entry side manifold and the power generation unit flow path to expand the flow from the manifold length to the entire width of the fuel cell power generation unit, and the flow between each output side manifold and the power generation unit flow path. The flow rectifier 36 is provided to reduce the fuel cell power generator from the full width to the manifold length. The cooling water channel, the fuel gas channel, and the air channel are sealed with each other. 3 in FIG. 3 is a sealing material for refrigerant sealing between modules.
[0015]
As shown in FIG. 3 (a cross section viewed along the line AA in FIG. 2), the gas flow path 27 or 28 is formed on one side, the refrigerant flow path 26 is formed on the other side, and the portion is formed by pressing. In the separators 18A and 18B, when the gas channel width (fuel gas channel width, oxidizing gas channel width) is d _G and the refrigerant channel width is d _W , these parameters are:
d _G ≧ d _W
Satisfied with the relationship. And pitch D (pitch of gas flow path = pitch of refrigerant flow path) is:
D = d _G + d _W
It is. In the above, the gas flow path width d _G and the refrigerant flow path width d _W are the midpoint of the flow path depth in the depth direction of the flow path (a point of 1 / 2h when the depth is h). The channel width or the channel width on the surface in contact with the MEA.
In the illustrated example, the separators 18A and 18B in which the gas flow path is formed on one surface and the refrigerant flow path is formed on the other surface are made of a metal that is a high heat conductive material.
[0016]
Next, the operation of the fuel cells having a metal separator of the present invention.
In the conventional separator has a d _G <d _W, the fuel cells having a metal separator of the present invention, because you have a d _G ≧ d _W, and the gas flow path width d _G is conventional and the present invention In the same case, the refrigerant flow path width d _W becomes smaller than the conventional one. Further, when the pitch D is the same between the present invention and the conventional one, the refrigerant flow path width d _W is smaller than the conventional one, and the gas flow path width d _G is larger than the conventional one.
[0017]
By reducing the refrigerant flow path width d _W , the area of the diffusion layers 13 and 16 pushed by the bottom part of the separator refrigerant flow channel groove decreases (the portion of the diffusion layer that has been pushed to increase the density has gas diffusibility. The area of the diffusion layer that is pushed and deteriorates in diffusibility decreases, and the area of the gas diffusion area to the catalyst layers 12 and 15 decreases, and as a result, power generation out of the cell area. The area of the portion (the catalyst layer portion where the gas is sufficiently diffused and supplied) is effectively increased.
Further, the coolant flow path width d _W is reduced, so that the amount of cooling water is reduced, the cell is not excessively cooled, the heat capacity of the cooling water is also reduced, and the controllability is improved. Further, by preventing excessive cooling, flooding in the downstream portion of the oxidizing gas due to the generated water is also suppressed. In the case of supercooling, the saturated vapor pressure is reduced and water is easily generated, but water generation can be suppressed by preventing overcooling.
[0018]
In the metal separators 18A and 18B, since the flow path forming portion is made of metal, since the metal has a large thermal conductivity and a relatively small heat capacity, the cooling tends to be excessive, but the condition of d _G ≧ d _W As long as the above is satisfied, the amount of cooling water is small and excessive cooling can be prevented.
[0019]
【The invention's effect】
According to fuel cells having a metal separator of claim 1, since the d _G ≧ d _W, may be smaller than a conventional refrigerant flow path width d _W.
By reducing the refrigerant flow path width, the area of the diffusion layer pushed by the separator refrigerant flow channel groove bottom is reduced, and the portion of the cell area that is effectively utilized for power generation (catalyst layer to which gas is sufficiently diffused and supplied) The area of the portion can be increased.
Moreover, since the cooling water flow amount is reduced by reducing the refrigerant flow path width, it is possible to eliminate the excessive cooling of the cell, to suppress flooding in the downstream portion of the oxidizing gas, and to improve the cooling controllability.
In addition, although the flow path forming portion is a high thermal conductive material, the condition of d _G ≧ d _W is satisfied, so the amount of cooling water is small and excessive cooling can be prevented.
[Brief description of the drawings]
FIG. 1 is an overall schematic view of a fuel cell provided with a metal separator of the present invention.
FIG. 2 is an exploded perspective view of one module of a fuel cell provided with the metal separator of the present invention.
FIG. 3 is an enlarged cross-sectional view of two modules of a part of a fuel cell provided with the metal separator of the present invention.
[Explanation of symbols]
10 (solid polymer electrolyte type) fuel cell 11 electrolyte membrane 12 catalyst layer 13 diffusion layer 14 electrode (anode, fuel electrode)
15 Catalyst layer 16 Diffusion layer 17 Electrode (cathode, air electrode)
18 Separator 18A Metal separator 18B that partitions fuel gas and cooling water Metal separator 18C that partitions oxidizing gas and cooling water Resin frame 18D Resin frame 19 Module 20 Terminal 21 Insulator 22 End plate 23 Stack 24 Fastening member (tension plate)
25 Bolt or nut 26 Refrigerant flow path (cooling water flow path)
27 Fuel gas flow path 28 Oxidizing gas flow path 30, 31 Opposing portion 32 Refrigerant (cooling water) manifold 32a Incoming refrigerant manifold 32b Outgoing refrigerant manifold 33 Fuel gas manifold 33a Incoming fuel gas manifold 33b Outgoing fuel Gas manifold 34 Oxidizing gas (air) manifold 34a Incoming oxidizing gas manifold 34b Outlet oxidizing gas manifold 35 Rectifier 36 Rectifier 37 Seal member (for refrigerant seal)

Claims (1)

Comprises a metal separator moiety is that is formed by a press having a portion where the refrigerant flow path is formed on the other surface gas flow path is formed on one surface, the metal separator is in contact with one another in the gas flow path groove bottom between modules In a fuel cell equipped with a metal separator,
The metal separator is
The gas flow path width is constant in the depth direction of the gas flow path except for the metal separator curved portions at both ends in the depth direction of the gas flow path,
The gas channel width d _G at the midpoint position of the gas channel depth and the refrigerant channel width d _W obtained by subtracting the gas channel width d _G from the gas channel pitch D are:
d _G ≧ d _W
Fuel cells having a metal separator, characterized in that satisfies the relationship.

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